U.S. patent application number 15/690710 was filed with the patent office on 2018-05-24 for detection device and sensor apparatus.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. The applicant listed for this patent is Kabushiki Kaisha Toshiba. Invention is credited to Yohei Hatakeyama, Tetsuro Itakura.
Application Number | 20180143020 15/690710 |
Document ID | / |
Family ID | 62146896 |
Filed Date | 2018-05-24 |
United States Patent
Application |
20180143020 |
Kind Code |
A1 |
Hatakeyama; Yohei ; et
al. |
May 24, 2018 |
DETECTION DEVICE AND SENSOR APPARATUS
Abstract
A detection device detects a dynamic quantity exerted on a
detection mechanical system including first and second mechanical
oscillators. The detection device includes first to third
transducers, a multiplication unit, a low-pass filter, and an
inverting amplification unit. The first transducer detects position
of the first mechanical oscillator in a first direction to output a
first signal. The second transducer detects position of the second
mechanical oscillator in a second direction to output a second
signal. The multiplication unit multiplies the signal that the
second transducer detects from the second mechanical oscillator by
the first signal before the signal is amplified. The third
transducer detects position of the second mechanical oscillator in
the second direction to output a third signal. The inverting
amplification unit gives a control signal generated by inverting
and simplifying the third signal to a second actuator that moves
the second mechanical oscillator in the second direction.
Inventors: |
Hatakeyama; Yohei;
(Yokohama, JP) ; Itakura; Tetsuro; (Nerima,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Toshiba |
Minato-ku |
|
JP |
|
|
Assignee: |
Kabushiki Kaisha Toshiba
Minato-ku
JP
|
Family ID: |
62146896 |
Appl. No.: |
15/690710 |
Filed: |
August 30, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01C 19/5776 20130101;
G01C 19/5621 20130101; G01C 19/56 20130101; G01C 19/5614 20130101;
B81B 2201/0242 20130101 |
International
Class: |
G01C 19/56 20060101
G01C019/56 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 21, 2016 |
JP |
2016-226295 |
Claims
1. A detection device that detects a dynamic quantity exerted on a
detection mechanical system, the detection mechanical system
including a first mechanical oscillator and a second mechanical
oscillator, the first mechanical oscillator being a mechanical
system held by a predetermined amount of spring force and capable
of reciprocating in a first direction, the second mechanical
oscillator being a mechanical system formed on a substrate on which
the first mechanical oscillator is formed, held by a predetermined
amount of spring force and capable of reciprocating in a second
direction perpendicular to the first direction, the detection
device comprising: a first transducer configured to detect a
position to which a first actuator makes the first mechanical
oscillator reciprocate in the first direction and amplify a
detected signal, so as to output a first positional signal
indicating the position of the first mechanical oscillator in the
first direction; a second transducer configured to detect a
position of the second mechanical oscillator in the second
direction and amplify a detected signal, so as to output a second
positional signal indicating the position of the second mechanical
oscillator in the second direction; a first multiplication unit
configured to multiply the signal that the second transducer
detects from the second mechanical oscillator by the first
positional signal before the signal is amplified; a low-pass filter
configured to remove a harmonic component from the second
positional signal, so as to output an output signal indicating a
detection result; a third transducer configured to detect a
position of the second mechanical oscillator in the second
direction and amplify a detected signal, so as to output a third
positional signal indicating the position of the second mechanical
oscillator in the second direction; and an inverting amplification
unit, configured to generate a control signal by inverting and
amplifying the third positional signal, and give the generated
control signal to the second actuator that moves the second
mechanical oscillator in the second direction.
2. The device according to claim 1, further comprising: a phase
adjustment unit configured to adjust a phase of the control signal
by an amount of phase corresponding to a response lag of the second
mechanical oscillator.
3. The device according to claim 1, wherein, according to the first
positional signal, the first multiplication unit varies a bias
voltage or bias current to be applied to a position detecting
device included in the second transducer.
4. The device according to claim 1, wherein, according to the
binary first positional signal, the first multiplication unit
inverts a direction in which a signal that the second transducer
detects from the second mechanical oscillator varies.
5. The device according to claim 1, further comprising: a control
unit configured to stop the first mechanical oscillator from
reciprocating in a period that is not a measurement period and make
the first mechanical oscillator reciprocate in the measurement
period by controlling a third actuator configured to stop the first
mechanical oscillator from moving in the first direction.
6. The device according to claim 5, wherein the control unit stops
controlling a position to which the second actuator moves the
second mechanical oscillator after a predetermined period of time
has passed since a measurement starts.
7. A sensor apparatus comprising: a detection mechanical system
including a first mechanical oscillator and a second mechanical
oscillator; and the detection device according to claim 1, the
detection device being configured to detect a dynamic quantity
exerted on the detection mechanical system.
8. The apparatus according to claim 7, wherein the first mechanical
oscillator, the second mechanical oscillator, a position detecting
device included in the first transducer, a position detecting
device included in the second transducer, and a position detecting
device included in the third transducer are formed on a
semiconductor substrate with Micro Electro Mechanical Systems
(MEMS) technology.
9. A device configured to detect a dynamic quantity exerted on as
detection mechanical system, the detection mechanical system
including a first mechanical oscillator and a second mechanical
oscillator, the first mechanical oscillator being a mechanical
system held by a predetermined amount of spring force and capable
of reciprocating in a first direction, the second mechanical
oscillator being a mechanical system formed on a substrate on which
the first mechanical oscillator is formed, held by a predetermined
amount of spring force and capable of reciprocating in a second
direction perpendicular to the first direction, the detection
device comprising: a first transducer configured to detect a
position to which a first actuator makes the first mechanical
oscillator reciprocate in the first direction and amplify a
detected signal, so as to output a first positional signal
indicating the position of the first mechanical oscillator in the
first direction; a second transducer configured to detect a
position of the second mechanical oscillator in the second
direction and amplify a detected signal, so as to output a second
positional signal indicating the position of the second mechanical
oscillator in the second direction; a first multiplication unit
configured to multiply the signal that the second transducer
detects from the second mechanical oscillator by the first
positional signal before the signal is amplified; a low-pass filter
configured to remove a harmonic component from the second
positional signal, so as to output an output signal indicating a
detection result; a second multiplication unit configured to
generate a modulated signal by multiplying the first positional
signal by the output signal; and an inverting amplification unit
configured to generate a control signal by inverting and amplifying
the modulated signal, and gives the generated control signal to the
second actuator that moves the second mechanical oscillator in the
second direction.
10. The device according to claim 9, further comprising: a phase
adjustment unit configured to adjust a phase of the control signal
by an amount of phase corresponding to a response lag of the second
mechanical oscillator.
11. The device according to claim 9, wherein, according to the
first positional signal, the first multiplication unit varies a
bias voltage or bias current to be applied to a position detecting
device included in the second transducer.
12. The device according to claim 9, wherein, according to the
binary first positional signal, the first multiplication unit
inverts a direction in which a signal that the second transducer
detects from the second mechanical oscillator varies.
13. The device according to claim 9, further comprising: a control
unit configured to stop the first mechanical oscillator from
reciprocating in a period that is not a measurement period and make
the first mechanical oscillator reciprocate in the measurement
period by controlling a third actuator configured to stop the first
mechanical oscillator from moving in the first direction.
14. The device according to claim 13, wherein the control unit
stops controlling a position to which the second actuator moves the
second mechanical oscillator after a predetermined period of time
has passed since a measurement starts.
15. A sensor apparatus comprising: a detection mechanical system
including a first mechanical oscillator and a second mechanical
oscillator; and the detection device according to claim 9, the
detection device being configured to detect a dynamic quantity
exerted on the detection mechanical system.
16. The apparatus according to claim 15, wherein the first
mechanical oscillator, the second mechanical oscillator, a position
detecting device included in the first transducer, a position
detecting device included in the second transducer, and a position
detecting device included in the third transducer are formed on a
semiconductor substrate with Micro Electro Mechanical Systems
(MEMS) technology.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2016-226295, filed on
Nov. 21, 2016; the entire contents of which are incorporated herein
by reference.
FIELD
[0002] Embodiments described herein relate generally to a detection
device and a sensor apparatus.
BACKGROUND
[0003] Vibratory gyroscopes manufactured with Micro Electro
Mechanical Systems (MEMS) technology are known.
[0004] Such a vibratory gyroscope includes a first mechanical
oscillator and a second mechanical oscillator. The first mechanical
oscillator is a mechanical system held with a predetermined amount
of spring force and capable of reciprocating in a first direction.
The second mechanical oscillator is a mechanical system formed on a
substrate on which the first mechanical oscillator is formed, held
with a predetermined amount of spring force, and capable of
reciprocating in a second direction perpendicular to the first
direction.
[0005] The first mechanical oscillator of the vibratory gyroscope
vibrates in the first direction. The Coriolis force acts in the
second direction in the vibratory gyroscope when the substrate
rotates around the axis perpendicular to both the first direction
and the second direction while the first mechanical oscillator
vibrates. The vibratory gyroscope detects the position of the
second mechanical oscillator in the second direction while the
first mechanical oscillator vibrates. This enables the vibratory
gyroscope to detect an angular rate around the direction
perpendicular to both the first direction and the second
direction.
[0006] The output signal from the vibratory gyroscope includes two
disturbances. One of the disturbances is quadrature error, and the
other is a step response. The quadrature error is generated when
the vibration of the first mechanical oscillator in the first
direction is exerted on the second mechanical oscillator. The
quadrature error is an error component having a phase difference of
.+-.90.degree. from a desired signal of the output signal. The
error component of the quadrature error has amplitude that is not
more than 10 times the output signal.
[0007] The step response is generated when the vibration of the
first mechanical oscillator is turned on/off. The error component
of the step response has amplitude that is not more than 100 times
the desired signal of the output signal.
[0008] Amplifying an output signal including such two disturbances
significantly decreases the signal-to-noise ratio (SNR) of the
output signal. Thus, an AD converter with a wide dynamic range is
required to detect the desired signal from such an output signal.
This requirement increases circuit power.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a view of a configuration of a sensor apparatus
according to a first embodiment;
[0010] FIG. 2 is a waveform chart, for example, of a disturbance
exerted on a second mechanical oscillator;
[0011] FIG. 3 is a block diagram of a transfer characteristic of
the sensor apparatus according to the first embodiment;
[0012] FIG. 4 is a view of a first example of a first
transducer;
[0013] FIG. 5 is a view of a second example of the first
transducer;
[0014] FIG. 6 is a view of a third example of the first
transducer;
[0015] FIG. 7 is a view of a fourth example of the first
transducer;
[0016] FIG. 8 is a view of a fifth example of the first
transducer;
[0017] FIG. 9 is a view of a first example of a bias-type first
multiplication unit and a second transducer;
[0018] FIG. 10 is a view of a second example of a bias-type first
multiplication unit and a second transducer;
[0019] FIG. 11 is a view of a third example of a bias-type first
multiplication unit and a second transducer;
[0020] FIG. 12 is a view of a fourth example of a bias-type first
multiplication unit and a second transducer;
[0021] FIG. 13 is a view of a fifth example of a switch-type first
multiplication unit and a second transducer;
[0022] FIG. 14 is a view of a sixth example of a switch-type first
multiplication unit and a second transducer;
[0023] FIG. 15 is a view of a seventh example of a switch-type
first multiplication unit and a second transducer;
[0024] FIG. 16 is a view of an eighth example of a switch-type
first multiplication unit and a second transducer;
[0025] FIG. 17 is a view of a configuration of a sensor apparatus
according to a second embodiment;
[0026] FIG. 18 is a block diagram of a transfer characteristic of
the sensor apparatus according to the second embodiment; and
[0027] FIG. 19 is a waveform chart, for example, of the timing for
switching loop gain.
DETAILED DESCRIPTION
[0028] According to an embodiment, a detection device detects a
dynamic quantity exerted on a detection mechanical system. The
detection mechanical system includes a first mechanical oscillator
and a second mechanical oscillator. The first mechanical oscillator
is a mechanical system held by a predetermined amount of spring
force and capable of reciprocating in a first direction. The second
mechanical oscillator is a mechanical system formed on a substrate
on which the first mechanical oscillator is formed, held by a
predetermined amount of spring force and capable of reciprocating
in a second direction perpendicular to the first direction. The
detection device includes a first transducer, a second transducer,
a first multiplication unit, a low-pass filter, a third transducer,
and an inverting amplification unit. The first transducer detects a
position to which a first actuator makes the first mechanical
oscillator reciprocate in the first direction and amplifies a
detected signal, so as to output a first positional signal
indicating the position of the first mechanical oscillator in the
first direction. The second transducer detects a position of the
second mechanical oscillator in the second direction and amplifies
a detected signal, so as to output a second positional signal
indicating the position of the second mechanical oscillator in the
second direction. The first multiplication unit multiplies the
signal that the second transducer detects from the second
mechanical oscillator by the first positional signal before the
signal is amplified. The low-pass filter removes a harmonic
component from the second positional signal, so as to output an
output signal indicating a detection result. The third transducer
detects a position of the second mechanical oscillator in the
second direction and amplifies a detected signal, so as to output a
third positional signal indicating the position of the second
mechanical oscillator in the second direction. The inverting
amplification unit generates a control signal by inverting and
amplifying the third positional signal, and gives the generated
control signal to the second actuator that moves the second
mechanical oscillator in the second direction.
First Embodiment
[0029] FIG. 1 is a view of a configuration of a sensor apparatus 10
according to a first embodiment. The sensor apparatus 10 accurately
detects a dynamic quantity. For example, the sensor apparatus 10 is
a vibratory gyroscope that accurately detects an angular rate.
[0030] The sensor apparatus 10 includes a detection mechanical
system 22 and a detection device 24.
[0031] The detection mechanical system 22 is a mechanical structure
for detecting a dynamic quantity. The detection mechanical system
22 is, for example, a semiconductor substrate formed with MEMS
technology and capable of mechanically operating. Note that the
detection mechanical system 22 is not necessarily a semiconductor
substrate, and may also be a module including same mechanical
components.
[0032] The detection device 24 is a device that detects a
mechanical behavior of the detection mechanical system 22 and
outputs an electrical signal. The detection device 24 is, for
example, an electrical circuit that is formed on a semiconductor
substrate and performs an electrical signal processing. The
detection device 24 may be implemented with a semiconductor
substrate, or with a plurality of semiconductor substrates.
Alternatively, the detection device 24 may be implemented with a
common semiconductor substrate shared with the detection mechanical
system 22.
[0033] The detection mechanical system 22 includes a first
mechanical oscillator 42 and a second mechanical oscillator 44. The
first mechanical oscillator 42 and the second mechanical oscillator
44 are formed on the same substrate. The first mechanical
oscillator 42 and the second mechanical oscillator 44 are formed,
for example, on a semiconductor substrate with MEMS technology.
[0034] The first mechanical oscillator 42 is a mechanical system
capable of reciprocating in a first direction. The first mechanical
oscillator 42 is held in the first direction by a predetermined
amount of spring force. The first mechanical oscillator 42 may
include an attenuation mechanical system that attenuates the
vibration in the first direction.
[0035] The second mechanical oscillator 44 is a mechanical system
capable of reciprocating in a second direction perpendicular to the
first direction. The second mechanical oscillator 44 is held in the
second direction by a predetermined amount of spring force. The
second mechanical oscillator 44 may include an attenuation
mechanical system that attenuates the vibration in the second
direction.
[0036] The first mechanical oscillator 42 and the second mechanical
oscillator 44 each include a moving structure having a
predetermined mass and capable of reciprocating, an elastic
material (for example, a spring) that vibrates the moving
structure, and an attenuation material (for example, a damper) that
attenuates the vibration of the moving structure. The attenuation
material may be, for example, air or a liquid.
[0037] The moving structure may be formed into a shape like a
tuning fork with MEMS technology. In other words, the moving
structure may be a plurality of vibration plates arranged in
parallel at predetermined intervals. One sides of the vibration
plates are fixed on the substrate. Such a moving structure includes
open ends on the vibration plates that vibrate in the direction in
which the vibration plates are arranged. The first mechanical
oscillator 42 including such a moving structure has a structure in
which the moving structure can move in the first direction. The
second mechanical oscillator 44 including such a moving structure
has a structure in which the moving structure can move in the
second direction.
[0038] The Coriolis force acts in the second direction in the
detection mechanical system 22 when the detection mechanical system
22 rotates around the direction perpendicular to both the first
direction and the second direction while the first mechanical
oscillator 42 vibrates in the first direction. The Coriolis force
corresponds to an angular rate of the detection mechanical system
22. The Coriolis force that acts in the detection mechanical system
22 as described above vibrates the second mechanical oscillator 44
in the second direction.
[0039] Note that the frequency of the resonance of the second
mechanical oscillator 44 is higher enough than the angular rate of
the detection mechanical system 22. Thus, the Coriolis force that
acts when the detection mechanical system 22 rotates does not
vibrate the second mechanical oscillator 44 at the resonance
point.
[0040] A detection device 24 includes an oscillation unit 46, a
first actuator 48, a first transducer 50, a first noise removing
filter 52, a second transducer 54, a first multiplication unit 56,
a low-pass filter 58, a third transducer 60, a second noise
removing filter 62, an inverting amplification unit 64, a phase
adjustment unit 66, a second actuator 68, a third actuator 70, and
a control unit 72.
[0041] The oscillation unit 46 outputs a periodic signal for
vibrating the first mechanical oscillator 42 in the first
direction. For example, the oscillation unit 46 outputs a periodic
signal at the frequency of the resonance value of the first
mechanical oscillator 42.
[0042] The first actuator 48 causes the first mechanical oscillator
42 to reciprocate in the first direction according to the periodic
signal output from the oscillation unit 46. For example, when the
frequency of the periodic signal is the resonance value of the
first mechanical oscillator 42, the first actuator 48 can vibrate
the first mechanical oscillator 42 at the resonance frequency. Note
that a part or the whole of the first actuator 48 may be included
in the detection mechanical system 22.
[0043] The first transducer 50 detects the position of the first
mechanical oscillator 42 in the first direction. Then, the first
transducer 50 amplifies a detected signal so as to output a first
positional signal indicating the position of the first mechanical
oscillator 42 in the first direction.
[0044] Note that the detection mechanical system 22 may include a
part of the first transducer 50. For example, the first transducer
50 includes a position detecting device for detecting the position
of the first mechanical oscillator 42 in the first direction. The
position detecting device may be formed, for example, in the
detection mechanical system 22 with MEMS technology.
[0045] For example, when the moving structure of the first
mechanical oscillator 42 is a plurality of vibration plates, the
position detecting device may include the vibration plates and, for
example, a detection plate. Note that, in such a case, the
vibration plates function as the first mechanical oscillator 42 and
also function as the position detecting device. The detection plate
is inserted into each gap between the vibration plates. The
distance between the detection plate and vibration plate of the
position detecting device varies when the vibration plate moves in
the first direction.
[0046] Such a position detecting device changes the capacitance
value between the detection plate and the vibration plate according
to the position of the vibration plate in the first direction when
the gap between the detection plate and the vibration plate
includes, for example, air. Alternatively, the position detecting
device changes the resistance value between the detection plate and
the vibration plate according to the position of the vibration
plate in the first direction when the gap between the detection
plate and the vibration plate includes, for example, a conductive
material. Alternatively, the position detecting device changes the
voltage between the detection plate and the vibration plate
according to the position of the vibration plate in the first
direction when the gap between the detection plate and the
vibration plate includes, for example, a material that generates a
voltage according to the pressure.
[0047] The first transducer 50 detects, for example, the
capacitance value, resistance value, or voltage value of the
position detecting device described above, using an electrical
circuit. Then, the first transducer 50 can output the first
positional signal indicating the position of the first mechanical
oscillator 42 in the first direction by amplifying the signal
indicating the detected capacitance value, resistance value, or
voltage value.
[0048] The first noise removing filter 52 removes a noise from the
first positional signal output from the first transducer 50. For
example, the first noise removing filter 52 may be a filter
circuit, for example, using an operational amplifier.
Alternatively, the detection device 24 may have a configuration
without the first noise removing filter 52. Alternatively, the
first noise removing filter 52 may be integrated with the
amplification unit included in the first transducer 50.
[0049] Note that the detection device 24 may feed the first
positional signal output from the first noise removing filter 52
back to the first actuator 48 as positive feedback. When the first
positional signal is fed back to the first actuator 48 as positive
feedback, the first actuator 48, the first mechanical oscillator
42, the first transducer 50, and the first noise removing filter 52
form an oscillator that oscillates at the resonance value of the
first mechanical oscillator 42. Thus, in this case, the detection
device 24 does not include the oscillation unit 46. Such a
detection device 24 can vibrate the first mechanical oscillator 42
with low energy.
[0050] The second transducer 54 detects the position of the second
mechanical oscillator 44 in the second direction. Then, the second
transducer 54 amplifies a detected signal so as to output a second
positional signal indicating the position of the second mechanical
oscillator 44 in the second direction.
[0051] Note that the detection mechanical system 22 may include a
part of the second transducer 54. For example, the second
transducer 54 includes a position detecting device for detecting
the position of the second mechanical oscillator 44 in the second
direction. The position detecting device may be formed, for
example, in the detection mechanical system 22 with MEMS
technology. Similarly to the position detecting device included in
the first transducer 50, the position detecting device may have a
configuration that changes the capacitance value, the resistance
value, or the voltage value.
[0052] The first multiplication unit 56 obtains the first
positional signal output from the first noise removing filter 52.
Then, the first multiplication unit 56 multiplies the signal that
the second transducer 54 detects from the second mechanical
oscillator 44 by the first positional signal before the signal is
amplified.
[0053] For example, when the second transducer 54 includes the
position detecting device that changes the capacitance value and
the resistance value, the first multiplication unit 56 varies the
bias voltage or bias current to be provided to the position
detecting device included in the second transducer 54 according to
the first positional signal. This enables the first multiplication
unit 56 to multiply the signal that the position detecting device
detects by the first positional signal before the signal is
amplified.
[0054] In addition, the first multiplication unit 56 inverts the
direction in which the signal that the second transducer 54 detects
from the second mechanical oscillator 44 varies, according to the
binary first positional signal. For example, when the second
transducer 54 outputs a differential signal, the first
multiplication unit 56 interchanges a signal line connected to a
positive input terminal of the amplification unit and a signal line
connected to a negative input terminal of the amplification unit
according to the binary first positional signal. This enables the
first multiplication unit 56 to multiply the signal that the second
transducer 54 detected from the second mechanical oscillator 44 by
the first positional signal.
[0055] The first positional signal is a signal indicating the
vibration of the first mechanical oscillator 42. In other words,
the first positional signal is a signal indicating quadrature error
to the output signal. In addition, the first multiplication unit 56
can remove a first positional signal from the signal output from
the second transducer 54 by multiplying the signal detected from
the second mechanical oscillator 44 by the first positional signal.
Thus, the first multiplication unit 56 enables the second
transducer 54 to output the second positional signal indicating the
desired signal from which the quadrature error is removed.
[0056] In addition, the first multiplication unit 56 performs the
multiplication of the first positional signal before the signal
amplification circuit of the second transducer 54. This enables the
first multiplication unit 56 to remove the disturbance from the
signal before the signal is amplified. This enables the second
transducer 54 to amplify the desired signal from which the
disturbance is removed. This improves the signal-to-noise ratio
(SNR) of the signal.
[0057] The low-pass filter 58 removes a harmonic component from the
second positional signal output from the second transducer 54. In
other words, the low-pass filter 58 removes the harmonic component
generated at the multiplication by the first positional signal.
Then, the second positional signal from which the harmonic
component is removed is output as an output signal indicating the
detection result. Note that the low-pass filter 58 may be
integrated with the amplification unit included in the second
transducer 54.
[0058] The third transducer 60 detects the position of the second
mechanical oscillator 44 in the second direction. Then, the third
transducer 60 amplifies a detected signal so as to output a third
positional signal indicating the position of the second mechanical
oscillator 44 in the second direction.
[0059] Note that the third transducer 60 is provided separately
from the second transducer 54. In addition, the detection
mechanical system 22 may include a part of the third transducer 60.
For example, the third transducer 60 includes a position detecting
device for detecting the position of the second mechanical
oscillator 44 in the second direction. The position detecting
device may be formed, for example, in the detection mechanical
system 22 with MEMS technology. Similarly to the position detecting
device of the first transducer 50, the position detecting device
may have a configuration that changes the capacitance value, the
resistance value, or the voltage value.
[0060] The second noise removing filter 62 removes a noise from the
third positional signal output from the third transducer 60. For
example, the second noise removing filter 62 may be a filter
circuit, for example, using an operational amplifier.
Alternatively, the detection device 24 may have a configuration
without the second noise removing filter 62. Alternatively, the
second noise removing filter 62 may be integrated with the
amplification unit included in the third transducer 60.
[0061] The inverting amplification unit 64 obtains the third
positional signal output from the second noise removing filter 62.
Then, the inverting amplification unit 64 generates a control
signal by inverting and amplifying the third positional signal.
[0062] The phase adjustment unit 66 obtains the control signal from
the inverting amplification unit 64. The phase adjustment unit 66
adjusts the phase of the control signal by the amount of phase
corresponding to the response lag in the second mechanical
oscillator 44. The amount of phase to be adjusted will be described
below with reference to FIG. 3. In addition, the detection device
24 may sometimes be without the phase adjustment unit 66. Such a
case will also be described below with reference to FIG. 3.
[0063] The second actuator 68 moves the second mechanical
oscillator 44 in the second direction according to the control
signal output from the phase adjustment unit 66.
[0064] For example, when the first mechanical oscillator 42
repeatedly turns a vibration period on and off (repeatedly turns an
angular rate measurement period on and off), the disturbance in the
step response is applied to the second mechanical oscillator 44.
However, the third transducer 60, the second noise removing filter
62, the inverting amplification unit 64, the phase adjustment unit
66, and the second actuator 68 detect the position to which the
second mechanical oscillator 44 is moved, and controls the position
to which the second mechanical oscillator 44 is moved using
negative feedback. This control enables the second mechanical
oscillator 44 to stably operate even if the disturbance in the step
response is applied. Accordingly, the detection device 24 can
output an output signal from which the disturbance in the step
response is removed. Note that a part or the whole of the second
actuator 68 may be included in the detection mechanical system
22.
[0065] The third actuator 70 stops the movement of the first
mechanical oscillator 42 in the first direction. For example, the
third actuator 70 gives force sufficiently stronger than the first
actuator 48 to the first mechanical oscillator 42 to forcibly stop
the movement of the first mechanical oscillator 42 even while the
force by the first actuator 48 is applied. Note that a part or the
whole of the third actuator 70 may be included in the detection
mechanical system 22.
[0066] The control unit 72 controls the third actuator 70 to make
the first mechanical oscillator 42 reciprocate during the
measurement period, and stop the reciprocation of the first
mechanical oscillator 42 during a period that is not a measurement
period.
[0067] FIG. 2 is a waveform chart of a CR signal, the vibration of
the first mechanical oscillator 42, and a disturbance exerted on
the second mechanical oscillator 44.
[0068] The control unit 72 gives the third actuator 70 a catch
command (a stop command) to stop the reciprocation of the first
mechanical oscillator 42 during a period that is not a measurement
period in which the angular rate of the detection mechanical system
22 is measured. Then, the control unit 72 gives the third actuator
70 a release command (movement allowance command) to start the
reciprocation of the first mechanical oscillator 42 during the
measurement period in which the angular rate of the detection
mechanical system 22 is measured. For example, as illustrated in A
of FIG. 2, the control unit 72 gives the third actuator 70 a
control signal repeating the catch command and the release
command.
[0069] As illustrated in B of FIG. 2, the first mechanical
oscillator 42 does not vibrate during the period in which the
control unit 72 outputs the catch command. The first mechanical
oscillator 42 vibrates during the period in which the control unit
72 outputs the release command. In other words, the first
mechanical oscillator 42 vibrates intermittently.
[0070] The second mechanical oscillator 44 receives the disturbance
in the step response caused by the intermittent operation of the
first mechanical oscillator 42. Thus, the second mechanical
oscillator 44 vibrates in response to the disturbance in the step
response at the resonance frequency of the second mechanical
oscillator 44 as illustrated in C of FIG. 2 unless any measure is
taken to remove the step response.
[0071] FIG. 3 is a block diagram of a transfer characteristic of
the sensor apparatus 10 according to the first embodiment in order
to remove the step response.
[0072] FIG. 3 illustrates an exemplary transfer characteristic of a
feedback system including the second mechanical oscillator 44, the
third transducer 60, the second noise removing filter 62, the
inverting amplification unit 64, the phase adjustment unit 66, and
the second actuator 68. The X indicates the disturbance exerted on
the second mechanical oscillator 44. The Y indicates the position
of the second mechanical oscillator 44 in the second direction. The
A indicates a resonance transfer function of a mechanical system of
the second mechanical oscillator 44. The B indicates a transfer
function of the second transducer 54, and the B is a constant. The
C indicates a transfer function of a feedback system from the third
transducer 60 to the second actuator 68, and the C is a
constant.
[0073] To simplify the transfer characteristic, the resonance
transfer function of the second mechanical oscillator 44 takes Q as
a gain (Q value) at the resonance frequency and takes one as the
gain at a frequency lower than the resonance frequency. In such a
case, the transfer function in FIG. 3 is Y/X=A/(1+AC).
[0074] It is assumed that the C is 1/100. In this case, the AC is
smaller enough than one. Thus, the transfer function is
Y/X=(A/(1+AC)).apprxeq.A at a frequency lower than the resonance
frequency. In contrast, A=Q holds and the A is larger enough than
one at the resonance frequency. Thus, the transfer function is
Y/X=(A/(1+AC)).apprxeq.1/C.
[0075] As described above, the transfer function shows that the
gain decreases at the resonance frequency. In contrast, the
transfer function shows that the gain does not decrease at
frequencies except for the resonance frequency.
[0076] Accordingly, the detection device 24 can decrease an
attenuation time constant by reducing the effective Q value of the
second mechanical oscillator 44 by 1/CQ. The frequency of the
Coriolis force that acts in the detection mechanical system 22 is
set at a frequency lower enough than the resonance frequency of the
second mechanical oscillator 44. Thus, the detection device 24 can
transfer the desired signal except for a signal at the resonance
frequency without attenuating the desired signal.
[0077] Furthermore, the phase adjustment unit 66 adjusts the phase
of the control signal by the amount of phase corresponding to the
response lag in the second mechanical oscillator 44.
[0078] The resonance transfer function of the mechanical system of
the second mechanical oscillator 44 (the A illustrated in FIG. 3)
is a second order lag system. Thus, the phase lag of the resonance
transfer function is 180.degree. at most. In general, the feedback
circuit oscillates when feeding the signal lagging 180.degree. back
as negative feedback. The phase adjustment unit 66 adjusts the
phase of the control signal to prevent the oscillation. For
example, the phase adjustment unit 66 differentiates the control
signal to adjust the range of the phase between -90.degree. and
+90.degree.. This adjustment enables the phase adjustment unit 66
to prevent the oscillation caused by the feedback of the
disturbance in the step response.
[0079] The phase adjustment unit 66 may be implemented, for
example, with an operational amplifier and a capacitor. The phase
adjustment unit 66 is not limited to such a configuration and may
have another configuration.
[0080] Note that the third transducer 60 may include a position
detecting device that detects a current from a variable capacitance
controlled at a constant voltage. The detection device 24 does not
necessarily include the phase adjustment unit 66 when including
such a third transducer 60.
[0081] When a constant voltage is applied to the variable
capacitance, the variable capacitance is electrically charged with
charge of Q=C.times.V. The slight change of the variable
capacitance makes .DELTA.Q=.DELTA.C.times.V hold. The current is
calculated from the differential value of the charge amount. In
other words, the current is calculated with
I=.DELTA.Q/.DELTA.t=.DELTA.C/.DELTA.t.times.V. Thus, when the third
transducer 60 detects the current from the position detecting
device (variable capacitance) controlled at a constant voltage, the
third transducer 60 of the detection device 24 has a
differentiating function. Thus, the detection device 24 without the
phase adjustment unit 66 can also adjust the range of the phase of
the control signal between -90.degree. and +90.degree..
[0082] As described above, the detection device 24 according to the
present embodiment can remove the quadrature error from the second
positional signal. With this removal, the detection device 24 can
also remove the disturbance in step response from the second
positional signal.
[0083] Thus, the detection device 24 can accurately detect the
dynamic quantity exerted on the detection mechanical system 22 with
a low power. For example, the detection device 24 can accurately
detects the angular rate exerted on the detection mechanical system
22 at a low power.
[0084] FIG. 4 illustrates a first example of the first transducer
50. The first transducer 50 according to the first example includes
a first position detecting device 112 and a first amplification
unit 114.
[0085] The first position detecting device 112 includes a first
variable resistance 120, and a second variable resistance 122. The
first amplification unit 114 includes a first differential
amplifier 124, a first resistance 126, and a second resistance
128.
[0086] The first variable resistance 120 is connected between power
source potential (VDD) and a positive input terminal of the first
differential amplifier 124. The second variable resistance 122 is
connected between power source potential (VDD) and a negative input
terminal of the first differential amplifier 124.
[0087] The first resistance 126 is connected between the positive
input terminal of the first differential amplifier 124 and a
positive output terminal of the first differential amplifier 124.
The second resistance 128 is connected between the negative input
terminal of the first differential amplifier 124 and a negative
output terminal of the first differential amplifier 124.
[0088] The first differential amplifier 124 outputs a differential
signal having a voltage difference corresponding to the difference
between the current flowing in the first variable resistance 120
and the current flowing in the second variable resistance 122.
[0089] The resistance value of each of the first variable
resistance 120 and the second variable resistance 122 varies
depending on the position of the first mechanical oscillator 42 in
the first direction. There is a potential difference of a common
potential (CM) between the positive input terminal and negative
input terminal of the first differential amplifier 124. The common
potential (CM) is, for example, a middle-point voltage (VDD/2)
between a ground potential (GND) and the power source potential
(VDD). Thus, the potential difference between the first variable
resistance 120 and the second variable resistance 122 is constantly
VDD/2. Thus, a change of the resistance value changes the flowing
current.
[0090] The direction in which the resistance value of the first
variable resistance 120 changes is opposite to the direction in
which the resistance value of the second variable resistance 122
changes. Accordingly, the first differential amplifier 124 can
output the differential signal having the voltage difference
corresponding to the position of the first mechanical oscillator 42
in the first direction. Note that the first transducer 50 according
to the first example is referred to as a resistive transducer.
[0091] FIG. 5 illustrates a second example of the first transducer
50. The first transducer 50 according to the second example
includes a second position detecting device 132 and a second
amplification unit 134.
[0092] The second position detecting device 132 includes a first
piezoelectric element 140, and a second piezoelectric element 142.
The second amplification unit 134 includes a first operational
amplifier 144, a second operational amplifier 146, a third
resistance 148, a fourth resistance 150, a fifth resistance 152,
and a sixth resistance 154.
[0093] The first piezoelectric element 140 is connected between
common potential (CM) and a non-inverting input terminal of the
first operational amplifier 144. The second piezoelectric element
142 is connected between common potential (CM) and a non-inverting
input terminal of the second operational amplifier 146.
[0094] The third resistance 148 is connected between an output
terminal of the first operational amplifier 144 and an inverting
input terminal of the first operational amplifier 144. The fourth
resistance 150 is connected between the inverting input terminal of
the first operational amplifier 144 and the common potential (CM).
The fifth resistance 152 is connected between an output terminal of
the second operational amplifier 146 and an inverting input
terminal of the second operational amplifier 146. The sixth
resistance 154 is connected between the inverting input terminal of
the second operational amplifier 146 and the common potential (CM).
A node connected to the first operational amplifier 144 of the
first piezoelectric element 140 is connected to the common
potential (CM) via as high-resistance element, for example. A node
connected to the second operational amplifier 146 of the second
piezoelectric element 142 is connected to the common potential (CM)
via a high-resistance element, for example.
[0095] The first operational amplifier 144 and the second
operational amplifier 146 output a differential signal having a
voltage corresponding the difference between the voltage applied to
the non-inverting input terminal of the first operational amplifier
144 and the voltage applied to the non-inverting input terminal of
the second operational amplifier 146.
[0096] The voltage value generated by each of the first
piezoelectric element 140 and the second piezoelectric element 142
changes depending on the position of the first mechanical
oscillator 42 in the first direction. The direction in which the
voltage value generated by the first piezoelectric element 140
changes is opposite to the direction in which the voltage value
generated by the second piezoelectric element 142 changes. Thus, a
voltage difference corresponding to the position of the first
mechanical oscillator 42 in the first direction is generated
between the output terminal of the first operational amplifier 144
and the output terminal of the second operational amplifier 146.
Thus, the first operational amplifier 144 and the second
operational amplifier 146 can output a differential signal having a
voltage corresponding to the position of the first mechanical
oscillator 42 in the first direction. Note that the first
transducer 50 according to the second example is referred to as a
piezoelectric transducer.
[0097] FIG. 6 illustrates a third example of the first transducer
50. The first transducer 50 according to the third example includes
a third position detecting device 162 and a third amplification
unit 164.
[0098] The third position detecting device 162 includes a first
variable capacitance 170, and a second variable capacitance 172.
The third amplification unit 164 includes a second differential
amplifier 174, a seventh resistance 176, and an eighth resistance
178.
[0099] The first variable capacitance 170 is connected between
ground potential (GND) and a positive input terminal of the second
differential amplifier 174. The second variable capacitance 172 is
connected between ground potential (GND) and a negative input
terminal of the second differential amplifier 174.
[0100] The seventh resistance 176 is connected between the positive
input terminal of the second differential amplifier 174 and a
positive output terminal of the second differential amplifier 174.
The eighth resistance 178 is connected between the negative input
terminal of the second differential amplifier 174 and a negative
output terminal of the second differential amplifier 174.
[0101] The second differential amplifier 174 outputs a differential
signal having a voltage corresponding to the difference between the
current flowing the first variable capacitance 170 and the current
flowing the second variable capacitance 172.
[0102] The capacitance value of each of the first variable
capacitance 170 and the second variable capacitance 172 changes
depending on the position of the first mechanical oscillator 42 in
the first direction. There is a potential difference of a common
potential (CM) between the positive input terminal and negative
input terminal of the second differential amplifier 174. Thus,
there is a constant potential difference between the first variable
capacitance 170 and the second variable capacitance 172. Thus, a
change of the capacitance value changes the flowing current.
[0103] The direction in which the capacitance value of the first
variable capacitance 170 changes is opposite to the direction in
which the capacitance value of the second variable capacitance 172
changes. Thus, the second differential amplifier 174 can output a
differential signal having a voltage corresponding to the position
of the first mechanical oscillator 42 in the first direction. Note
that the first transducer 50 according to the third example is
referred to as a capacitive transducer.
[0104] FIG. 7 illustrates a fourth example of the first transducer
50. The first transducer 50 according to the fourth example
includes a fourth position detecting device 182, and a fourth
amplification unit 184.
[0105] The fourth position detecting device 182 includes a third
variable capacitance 190, and a fourth variable capacitance 192.
The fourth amplification unit 184 includes a third operational
amplifier 194, a fourth operational amplifier 196, a ninth
resistance 198, a tenth resistance 200, an eleventh resistance 202,
a twelfth resistance 204, a first switch 206, a second switch 208,
a first fixed capacitance 210, and a second fixed capacitance
212.
[0106] The third variable capacitance 190 includes an end connected
to ground potential (GND). The fourth variable capacitance 192
includes an end connected to ground potential (GND). A node
connected to the third operational amplifier 194 of the first fixed
capacitance 210 and a node connected to the fourth operational
amplifier 196 of the second fixed capacitance 212 are each
connected to common potential (CM), via a high-resistance element,
for example.
[0107] The ninth resistance 198 is connected between an output
terminal of the third operational amplifier 194 and an inverting
input terminal of the third operational amplifier 194. The tenth
resistance 200 is connected between the inverting input terminal of
the third operational amplifier 194 and common potential (CM). The
eleventh resistance 202 is connected between an output terminal of
the fourth operational amplifier 196 and an inverting input
terminal of the fourth operational amplifier 196. The twelfth
resistance 204 is connected between the inverting input terminal of
the fourth operational amplifier 196 and common potential (CM).
[0108] The first switch 206 is connected between an end of the
third variable capacitance 190 that is not connected to ground
potential (GND) and power source potential (VDD). The second switch
208 is connected between an end of the fourth variable capacitance
192 that is not connected to ground potential (GND) and power
source potential (VDD).
[0109] The first fixed capacitance 210 is connected between the end
of the third variable capacitance 190 that is not connected to
ground potential (GND) and a non-inverting input terminal of the
third operational amplifier 194. The second fixed capacitance 212
is connected between the end of the fourth variable capacitance 192
that is not connected to ground potential (GND) and a non-inverting
input terminal of the fourth operational amplifier 196.
[0110] The first switch 206 and the second switch 208 are
periodically turned on and electrically charge the third variable
capacitance 190 and the fourth variable capacitance 192 with a
constant amount of charge. The first switch 206 and the second
switch 208 are turned off during the measurement period. Thus, a
constant amount of charge is accumulated in each of the third
variable capacitance 190 and the fourth variable capacitance 192
during the measurement period.
[0111] The third operational amplifier 194 and the fourth
operational amplifier 196 output as differential signal having a
voltage corresponding to the difference between the voltage applied
to the non-inverting input terminal of the third operational
amplifier 194 and the voltage applied to the non-inverting input
terminal of the fourth operational amplifier 196.
[0112] The capacitance value of each of the third variable
capacitance 190 and the fourth variable capacitance 192 changes
depending on the position of the first mechanical oscillator 42 in
the first direction. A change of the capacitance value of each of
the third variable capacitance 190 and the fourth variable
capacitance 192 changes the generated voltage because the amount of
charge is constant.
[0113] The direction in which the capacitance value of the third
variable capacitance 130 changes is opposite to the direction in
which the capacitance value of the fourth variable capacitance 192
changes. Thus, a voltage difference corresponding to the position
of the first mechanical oscillator 42 in the first direction is
generated between the output terminal of the third operational
amplifier 194 and the output terminal of the fourth operational
amplifier 196. Thus, the first operational amplifier 144 and the
second operational amplifier 146 can output a differential signal
having a voltage difference corresponding to the position of the
first mechanical oscillator 42 in the first direction. Note that
the first transducer 50 according to the fourth example is referred
to as a charge-fixed transducer.
[0114] FIG. 8 illustrates a fifth example of the first transducer
50. The first transducer 50 according to the fifth example includes
a fifth position detecting device 222, and a fifth amplification
unit 224.
[0115] The fifth position detecting device 222 includes a fifth
variable capacitance 232, and a sixth variable capacitance 234. The
fifth amplification unit 224 includes a third switch 236, a fourth
switch 238, a fifth switch 240, a sixth switch 242, a third
differential amplifier 244, a thirteenth resistance 246, and a
fourteenth resistance 248.
[0116] The third switch 236 and the fifth switch 240 are connected
in series between common potential (CM) and power source potential
(VDD). The fourth switch 238 and the sixth switch 242 are connected
in series between common potential (CM) and power source potential
(VDD).
[0117] The fifth variable capacitance 232 is connected between a
connection point of the third switch 236 with the fifth switch 240
and a positive input terminal of the third differential amplifier
244. The sixth variable capacitance 234 is connected between a
connection point of the fourth switch 238 with the sixth switch 242
and a negative input terminal of the third differential amplifier
244.
[0118] The thirteenth resistance 246 is connected between the
positive input terminal of the third differential amplifier 244 and
a positive output terminal of the third differential amplifier 244.
The fourteenth resistance 248 is connected between the negative
input terminal of the third differential amplifier 244 and a
negative output terminal of the third differential amplifier
244.
[0119] The third differential amplifier 244 outputs a differential
signal having a voltage corresponding to the difference between the
current flowing in the fifth variable capacitance 232 and the
current flowing in the sixth variable capacitance 234.
[0120] For example, the control unit 72 repeats the measurement
period and a discharge period, alternately. In the measurement
period, the third switch 236 and the fourth switch 238 are turned
on and the fifth switch 240 and the sixth switch 242 are turned
off. In the discharge period, the third switch 236 and the fourth
switch 238 are turned off and the fifth switch 240 and the sixth
switch 242 are turned on. For example, the control unit 72 repeats
the measurement period and the discharge period in a cycle enough
shorter than a vibration cycle in which the first mechanical
oscillator 42 vibrates.
[0121] The capacitance value of each of the fifth variable
capacitance 232 and the sixth variable capacitance 234 changes
depending on the position of the first mechanical oscillator 42 in
the first direction. There is a potential difference of a common
potential (CM) between the positive input terminal and negative
input terminal of the third differential amplifier 244. Thus, there
is a constant potential difference between the fifth variable
capacitance 232 and the sixth variable capacitance 234 during the
measurement period. Thus, a change of the capacitance value changes
the flowing current.
[0122] The direction in which the capacitance value of the fifth
variable capacitance 232 changes is opposite to the direction in
which the capacitance value of the sixth variable capacitance 234
changes. Thus, the third differential amplifier 244 can output a
differential signal having a voltage corresponding to the position
of the first mechanical oscillator 42 in the first direction during
the measurement period. Note that the first transducer 50 according
to the fifth example is referred to as a switched-capacitor
transducer.
[0123] The examples of the circuit of the first transducer 50 have
been described above with reference to FIG. 4 to FIG. 8. The third
transducer 60 may have the same configuration as that of the first
transducer 50. Note that if the third transducer 60 is a
capacitance and a switched-capacitor transducer, the third
transducer 60 has a differentiating function. In such a case, the
detection device 24 may have a configuration without the phase
adjustment unit 66.
[0124] Each of the amplification units (the first amplification
unit 114, the second amplification unit 134, the third
amplification unit 164, the fourth amplification unit 184, and the
fifth amplification unit 224) of the first transducer 50 described
with reference to FIG. 4 to FIG. 8 may have a configuration
including impedance instead of the resistance. The first transducer
50 described with reference to FIG. 4 to FIG. 8 may have a
configuration in which each of the amplification units (the first
amplification unit 114, the second amplification unit 134, the
third amplification unit 164, the fourth amplification unit 184,
and the fifth amplification unit 224) is integrated with the
following first noise removing filter 52. In such a case, for
example, each of the amplification units has a configuration that
removes a signal in a specific frequency band using impedance
instead of the resistance.
[0125] FIG. 9 illustrates a first example of a bias-type first
multiplication unit 56 and a second transducer 54. The second
transducer 54 according to the first example has approximately the
same configuration as the resistance first transducer 50
illustrated in FIG. 4. Thus, the same components will be put with
the same reference signs and the descriptions will be omitted.
[0126] The first multiplication unit 56 according to the first
example includes a voltage generation unit 302. The voltage
generation unit 302 generates a voltage corresponding to the first
positional signal output from the first noise removing filter 52
around common potential (CM).
[0127] The first position detecting device 112 of the second
transducer 54 according to the first example operates by the
voltage generated by the voltage generation unit 302 instead of
power source potential (VDD). In other words, the first variable
resistance 120 is connected between a voltage output end of the
voltage generation unit 302 and a positive input terminal of the
first differential amplifier 124. The second variable resistance
122 is connected between the voltage output end of the voltage
generation unit 302 and a negative input terminal of the first
differential amplifier 124.
[0128] The first multiplication unit 56 according to the first
example can vary the bias voltage to be applied to the first
position detecting device 112 included in the second transducer 54
according to the first positional signal. As a result, the first
multiplication unit 56 according to the first example can multiply
the signal that the second transducer 54 detects from the second
mechanical oscillator 44 by the first positional signal before the
first amplification unit 114.
[0129] FIG. 10 illustrates a second example of a bias-type first
multiplication unit 56 and a second transducer 54. The second
transducer 54 according to the second example has approximately the
same configuration as the capacitance first transducer 50
illustrated in FIG. 6. Thus, the same components will be put with
the same reference signs and the descriptions will be omitted.
[0130] The first multiplication unit 56 according to the second
example includes a voltage generation unit 302. The voltage
generation unit 302 has the same configuration as the configuration
illustrated in FIG. 9.
[0131] A third position detecting device 162 of the second
transducer 54 according to the second example operates based on the
voltage generated by the voltage generation unit 302. In other
words, the first variable capacitance 170 is connected between a
voltage output end of the voltage generation unit 302 and a
positive input terminal of the second differential amplifier 174.
The second variable capacitance 172 is connected between the
voltage output end of the voltage generation unit 302 and a
negative input terminal of the second differential amplifier
174.
[0132] Such a first multiplication unit 56 according to the second
example can vary the bias voltage to be applied to the third
position detecting device 162 included in the second transducer 54
according to the first positional signal. As a result, the first
multiplication unit 56 according to the second example can multiply
the signal that the second transducer 54 detects from the second
mechanical oscillator 44 by the first positional signal before the
third amplification unit 164.
[0133] FIG. 11 illustrates a third example of a bias-type first
multiplication unit 56 and a second transducer 54. The second
transducer 54 according to the third example has approximately the
same configuration as the charge-fixed first transducer 50
illustrated in FIG. 7. Thus, the same components will be put with
the same reference signs and the descriptions will be omitted.
[0134] The first multiplication unit 56 according to the third
example includes a voltage generation unit 302. The voltage
generation unit 302 has the same configuration as the configuration
illustrated in FIG. 9.
[0135] Charge is accumulated in the fourth position detecting
device 182 of the second transducer 54 according to the third
example by the voltage generated by the voltage generation unit 302
via a switch instead of power source potential (VDD). In other
words, the first switch 206 is connected between an end of the
third variable capacitance 190 that is not connected to ground
potential (GND) and at voltage output end of the voltage generation
unit 302. The second switch 208 is connected between an end of the
fourth variable capacitance 192 that is not connected to ground
potential (GND) and the voltage output end of the voltage
generation unit 302.
[0136] Such a first multiplication unit 56 according to the third
example can vary the bias voltage to be applied to the fourth
position detecting device 182 included in the second transducer 54
according to the first positional signal. As a result, the charge
varying according to the first positional signal is accumulated in
the third variable capacitance 190 and the fourth variable
capacitance 192. Thus, the first multiplication unit 56 according
to the third example can multiply the signal that the second
transducer 54 detects from the second mechanical oscillator 44 by
the first positional signal before the fourth amplification unit
184.
[0137] FIG. 12 illustrates a fourth example of a bias-type first
multiplication unit 56 and a second transducer 54. The second
transducer 54 according to the fourth example has approximately the
same configuration as the switched-capacitor first transducer 50
illustrated in FIG. 8. Thus, the same components will be put with
the same reference signs and the descriptions will be omitted.
[0138] The first multiplication unit 56 according to the fourth
example includes a voltage generation unit 302. The voltage
generation unit 302 has the same configuration as the configuration
illustrated in FIG. 9.
[0139] Charge is accumulated in a fifth position detecting device
222 of the second transducer 54 according to the fourth example by
the voltage generated by the voltage generation unit 302 via a
switch instead of power source potential (VDD). In other words, a
third switch 236 is connected between a fifth variable capacitance
232 and a voltage output end of the voltage generation unit 302. A
fourth switch 238 is connected between a sixth variable capacitance
234 and the voltage output end of the voltage generation unit
302.
[0140] Such a first multiplication unit 56 according to the fourth
example can vary the bias voltage to be applied to the fifth
position detecting device 222 included in the second transducer 54
according to the first positional signal. As a result, the charge
corresponding to the first positional signal is accumulated in the
fifth variable capacitance 232 and the sixth variable capacitance
234 during the measurement period. In other words, the current
corresponding to the first positional signal flows in the fifth
variable capacitance 232 and the sixth variable capacitance 234
during the measurement period. Thus, the first multiplication unit
56 according to the fourth example can multiply the signal that the
second transducer 54 detects from the second mechanical oscillator
44 by the first positional signal before the fifth amplification
unit 224.
[0141] FIG. 13 illustrates a fifth example of a switch-type first
multiplication unit 56 and a second transducer 54. The second
transducer 54 according to the fifth example has approximately the
same configuration as the resistance first transducer 50
illustrated in FIG. 4. Thus, the same components will be put with
the same reference signs and the descriptions will be omitted.
[0142] The first multiplication unit 56 according to the fifth
example includes a switching unit 312. The switching unit 312 is a
cross-point switch of two signal lines. In other words, the
switching unit 312 is a switch that interchanges the signal
circuits of the two signal lines.
[0143] The switching unit 312 according to the fifth example
interchanges a signal line connected to a positive input terminal
of as first differential amplifier 124 and a signal line connected
to a negative input terminal of the first differential amplifier
124 according to a binary first positional signal. This enables the
switching unit 312 to invert the positive part and negative part of
the differential signal output from the first differential
amplifier 124 according to the binary first positional signal. If
the positive part and negative part of the differential signal
output from the first differential amplifier 124 are inverted, the
direction in which the signal varies is inverted.
[0144] As described above, the first multiplication unit 56
according to the fifth example can invert the direction in which
the signal that the second transducer 54 detects from the second
mechanical oscillator 44 varies according to the first positional
signal. This enables the first multiplication unit 56 according to
the fifth example to multiply the signal that the second transducer
54 detects from the second mechanical oscillator 44 by the first
positional signal before the first amplification unit 114.
[0145] FIG. 14 illustrates a sixth example of a switch-type first
multiplication unit 56 and as second transducer 54. The second
transducer 54 according to the sixth example has approximately the
same configuration as the piezoelectric first transducer 50
illustrated in FIG. 5. Thus, the same components will be put with
the same reference signs and the descriptions will be omitted.
[0146] The first multiplication unit 56 according to the sixth
example includes a switching unit 312. The switching unit 312 has
the same configuration as the configuration illustrated in FIG.
13.
[0147] The switching unit 312 according to the sixth example
interchanges a signal line connected to a non-inverting input
terminal of a first operational amplifier 144 and a signal line
connected to a non-inverting input terminal of the second
operational amplifier 146 according to a binary first positional
signal. This enables the switching unit 312 to invert the positive
part and negative part of the differential voltage between an
output terminal of the first operational amplifier 144 and an
output terminal of the second operational amplifier 146 according
to the binary first positional signal.
[0148] As described above, the first multiplication unit 56
according to the sixth example can invert the direction in which
the signal that the second transducer 54 detects from the second
mechanical oscillator 44 varies according to the first positional
signal. This enables the first multiplication unit 56 according to
the sixth example to multiply the signal that the second transducer
54 detects from the second mechanical oscillator 44 by the first
positional signal before the second amplification unit 134.
[0149] FIG. 15 illustrates a seventh example of a switch-type first
multiplication unit 56 and a second transducer 54. The second
transducer 54 according to the seventh example has approximately
the same configuration as the charge-fixed first transducer 50
illustrated in FIG. 7. Thus, the same components will be put with
the same reference signs and the descriptions will be omitted.
[0150] The first multiplication unit 56 according to the seventh
example includes a switching unit 312. The switching unit 312 has
the same configuration as the configuration illustrated in FIG.
13.
[0151] The switching unit 312 according to the seventh example
interchanges a signal line connected to as non-inverting input
terminal of a third operational amplifier 194 and a signal line
connected to a non-inverting input terminal of a fourth operational
amplifier 196 according to a binary first positional signal. This
enables the switching unit 312 to invert the positive part and
negative part of the differential voltage between an output
terminal of the third operational amplifier 194 and an output
terminal of the fourth operational amplifier 196 according to the
binary first positional signal.
[0152] As described above, the first multiplication unit 56
according to the seventh example can invert the direction in which
the signal that the second transducer 54 detects from the second
mechanical oscillator 44 varies according to the first positional
signal. This enables the first multiplication unit 56 according to
the seventh example to multiply the signal that the second
transducer 54 detects from the second mechanical oscillator 44 by
the first positional signal before the fourth amplification unit
184.
[0153] FIG. 16 illustrates an eighth example of a switch-type first
multiplication unit 56 and a second transducer 54. The second
transducer 54 according to the eighth example has approximately the
same configuration as the switched-capacitor first transducer 50
illustrated in FIG. 8. Thus, the same components will be put with
the same reference signs and the descriptions will be omitted.
[0154] The first multiplication unit 56 according to the eighth
example includes a switching unit 312. The switching unit 312 has
the same configuration as the configuration illustrated in FIG.
13.
[0155] The switching unit 312 according to the eighth example
interchanges a signal line connected to a positive input terminal
of a third differential amplifier 244 and a signal line connected
to a negative input terminal of the third differential amplifier
244 according to a binary first positional signal. This enables the
switching unit 312 to invert the positive part and negative part of
the differential signal output from the third differential
amplifier 244 according to the binary first positional signal.
[0156] As described above, the first multiplication unit 56
according to the eighth example can invert the direction in which
the signal that the second transducer 54 detects from the second
mechanical oscillator 44 varies according to the first positional
signal. This enables the first multiplication unit 56 according to
the eighth example to multiply the signal that the second
transducer 54 detects from the second mechanical oscillator 44 by
the first positional signal before the fifth amplification unit
224.
Second Embodiment
[0157] FIG. 17 illustrates a configuration of a sensor apparatus 10
according to a second embodiment. The sensor apparatus 10 according
to the second embodiment includes approximately the same functions
and configuration as the sensor apparatus 10 according to the first
embodiment. In the description of the second embodiment, the blocks
having approximately the same functions and configurations as the
blocks described in the first embodiment will be put with the same
reference signs and the descriptions will be omitted except for the
descriptions of different points.
[0158] A detection device 24 according to the second embodiment
includes an oscillation unit 46, a first actuator 48, a first
transducer 50, a first noise removing filter 52, a second
transducer 54, a first multiplication unit 56, a low-pass filter
58, a second multiplication unit 80, an inverting amplification
unit 64, a phase adjustment unit 66, a second actuator 68, a third
actuator 70, and a control unit 72. In other words, the detection
device 24 further includes the second multiplication unit 80 but
does not include the third transducer 60 and the second noise
removing filter 62 in comparison with the first embodiment.
[0159] The second multiplication unit 80 obtains a first positional
signal output from the first noise removing filter 52. The second
multiplication unit 80 further obtains an output signal output from
the low-pass filter 58. Then, the second multiplication unit 80
generates a modulated signal by multiplying the first positional
signal by the output signal.
[0160] The second multiplication unit 80 may generate the modulated
signal by multiplying the signal with an analog circuit such as an
operational amplifier. Alternatively, the second multiplication
unit 80 may generate the modulated signal by obtaining a binary
first positional signal and switching the positive part and
negative part of the output signal according to the binary first
positional signal.
[0161] The inverting amplification unit 64 obtains the modulated
signal from the second multiplication unit 80. The inverting
amplification unit 64 generates a control signal by inverting and
amplifying the modulated signal.
[0162] The detection device 24 according to the second embodiment
can detect the position to which the second mechanical oscillator
44 is moved, and control the position to which the second
mechanical oscillator 44 is moved using negative feedback. This
enables the second mechanical oscillator 44 to stably operate even
when the disturbance in step response is exerted. Thus, the
detection device 24 can output an output signal from which the
disturbance in step response is removed.
[0163] FIG. 18 is a block diagram of a transfer characteristic of
the sensor apparatus 10 according to the second embodiment in order
to remove step response.
[0164] FIG. 18 illustrates an exemplary transfer characteristic of
a feedback system constituted by the second mechanical oscillator
44, the second transducer 54, the low-pass filter 58, the second
multiplication unit 80, the inverting amplification unit 64, the
phase adjustment unit 66, and the second actuator 68. The X
indicates a disturbance exerted on the second mechanical oscillator
44. The Y indicates an output from the low-pass filter 58. The D
indicates a resonance transfer function of a mechanical system of
the second mechanical oscillator 44. The E indicates a transfer
function of the second transducer 54, and the E is a constant. The
F indicates a transfer function of a feedback system from the
second multiplication unit 80 to the second actuator 68, and the F
is a constant.
[0165] To simplify the transfer characteristic, the resonance
transfer function of the second mechanical oscillator 44 takes Q as
a gain (Q value) at a resonance frequency, and takes one as the
gain at a frequency lower than the resonance frequency. In such a
case, the transfer function in FIG. 18 is Y/X=DE/(1+DEF).
[0166] It is assumed that the EF is 1/100. In this case, the DEF is
smaller enough than one. Thus, the transfer function is
Y/X=(DE/(1+DEF)).apprxeq.DE at a frequency lower than the resonance
frequency. In contrast, D=Q holds and the D is larger enough than
one at the resonance frequency. Thus, the transfer function is
Y/X=(DE/(1+DEF)).apprxeq.1/EF.
[0167] As described above, the transfer function shows that the
gain decreases at the resonance frequency. In contrast, the
transfer function shows that the gain does not decrease at
frequencies except for the resonance frequency.
[0168] Accordingly, the detection device 24 can decrease an
attenuation time constant by reducing the effective Q value of the
second mechanical oscillator 44 by 1/EFQ. The frequency of the
Coriolis force that acts in the detection mechanical system 22 is
set at a frequency lower enough than the resonance frequency of the
second mechanical oscillator 44. Thus, the detection device 24 can
transfer the desired signal except for a signal at the resonance
frequency without attenuating the desired signal.
[0169] FIG. 19 is a waveform chart of a CR signal, the vibration of
the first mechanical oscillator 42, the disturbance exerted on the
second mechanical oscillator 44, and the timing at which loop gain
is switched. The control unit 72 may switch, for example, the gain
of the inverting amplification unit 64. For example, the control
unit 72 may be able to turn the loop gain of the feedback loop on
and off.
[0170] For example, as illustrated in D of FIG. 19, the control
unit 72 turns on the loop gain of the feedback loop at the timing
when a measurement starts in order to start controlling the
position to which the second actuator 68 moves the second
mechanical oscillator 44. Then, for example, the control unit 72
turns off the loop gain of the feedback loop after a predetermined
period of time has passed since the start of the measurement in
order to stop controlling the position to which the second actuator
68 moves the second mechanical oscillator 44.
[0171] A disturbance (a disturbance in step response), which is
exerted on the second mechanical oscillator 44 when the first
mechanical oscillator 42 intermittently operates, starts when the
first mechanical oscillator 42 starts vibrating and then
attenuates. Thus, the disturbance in step response decreases enough
after a certain period of time has passed since the start of the
vibration of the first mechanical oscillator 42. The control unit
72 stops controlling the position to which the second actuator 68
moves the second mechanical oscillator 44 after a predetermined
period of time has passed since the start of measurement. This
enables the control unit 72 to reduce the electricity consumption
by disabling the feedback loop after the disturbance in step
response decreases.
[0172] Note that the control unit 72 having the configuration
described in the first embodiment may also perform such a control.
Thus, in the configuration described in the first embodiment, the
control unit 72 can also reduce the electricity consumption by
disabling the feedback loop after the disturbance in step response
decreases.
[0173] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *